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slevis-lmwg · Sep 7, 2024 · 0c68f2e · 0c68f2e
1 parent 10319de
commit 0c68f2e
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/tools/mksurfdata_esmf/src/mksoiltexMod.F90 b/tools/mksurfdata_esmf/src/mksoiltexMod.F90
@@ -205,6 +205,10 @@ subroutine mksoiltex(file_mesh_i, file_mapunit_i, file_lookup_i, mesh_o, pioid_o
 
     ! Determine mapunit_value_max (set it as a module variable so that it can be
     ! accessible to gen_dominant_mapunit) - this is needed in the dynamic mask routine
+    !
+    ! Note that dataptr (obtained from the input field) contains just a subset of the
+    ! source data, based on the source data decomposition. So we need an mpi_allreduce to
+    ! determine the global maximum value of mapunit.
     mapunit_value_max_local = maxval(dataptr)
     call mpi_allreduce(mapunit_value_max_local, mapunit_value_max, 1, MPI_INTEGER, MPI_MAX, mpicom, rcode)